Decoding devices are known which are designed to initiate the operation of electromechanical equipment, sound a warning, or perform any similar function capable of electrical initiation, upon receipt of the proper coded signal.
A multifrequency signaling receiver for such purposes is shown, for example, in U.S. Pat. No. 3,281,790, issued 25 Oct. 1966 to L. C. J. Roscoe et al., and a transistorized device for similar purposes is the subject of U.S. Pat. No. 3,287,701, issued 22 Nov. 1966.
Prior systems have, in some instances, been susceptible to operation by random signalling, active jamming, etc., and none are known which have been designed to prevent unauthorized operation even by persons possessing knowledge of the mode of operation.
The device according to the present invention is constructed to not only be incapable of operation by random signalling but also to make operation of the system by unauthorized persons so extremely improbable as to be practically impossible even though such persons possess knowledge of the frequencies involved and the mode of operation of the device.
The Decoding Logic System according to the invention was developed as the result of a need for a small, light unit which could be left in remote locations to initiate operation of various devices at a later time by remote control. Reliability of operation was considered important but equally important was the need to prevent unauthorized persons from prematurely actuating the devices.
The device of the present invention achieves its purpose with only relatively small power and space requirements and may be inexpensively manufactured in quantity.